Why is sugar harmful to the brain?

The brain consumes up to 20–25% of the body's total energy. However, it has no glycogen reserves (unlike the liver and muscles). Therefore, glucose must continuously enter the bloodstream.

Internal regulation of sugar (endogenous glucose)

The body produces glucose itself:

• The liver breaks down glycogen (glycogenolysis),
• In case of carbohydrate deficiency, gluconeogenesis is initiated – the formation of glucose from amino acids, glycerol, and lactate.

This is a finely regulated process. The brain "monitors" through hormonal signals (insulin, glucagon, cortisol, adrenaline) and nerve impulses to keep blood sugar levels within a narrow corridor – about 4–5.5 mmol/L while fasting.

Why external sugar interferes

When a person eats sweets or foods with fast carbohydrates:

• The blood glucose level rises sharply,
• The pancreas is forced to release a lot of insulin,
• The brain receives a signal "too much sugar" and blocks internal glucose production.

However:

• Due to excess insulin, sugar quickly falls below normal (reactive hypoglycemia),
• The brain again experiences "energy hunger" and provokes cravings for sweets.

Thus, external sugar disrupts the precise mechanisms of self-regulation.

Consequences for the brain:

• Insulin resistance in the brain – cells absorb glucose worse, leading to chronic fatigue and memory decline.
• Glycation of proteins (for example, the formation of glycated hemoglobin) damages blood vessels and neurons.
• Oxidative stress – rapid sugar spikes increase the formation of free radicals.
• Disruption of neurotransmitters: excess sugar reduces the sensitivity of dopamine receptors → dependence on sweets.

Why natural regulation is better

When glucose is formed from internal sources:

• Its level is smooth, without sharp spikes,
• The brain receives a steady flow of energy,
• The load on blood vessels and the pancreas is reduced,
• Insulin sensitivity and healthy neurotransmitter exchange are maintained.

External sugar, especially in excessive amounts, disrupts the delicate control system, disturbs the balance of hormones and neurotransmitters, and over time leads to metabolic disorders.